Tablet coating method



United States Patent 3,185,626 TABLET CGATING METHOD Claude W. Baker, Albany, N.Y., assigner to Sterling Drug Inc, New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 6, 1963, Ser. No. 263,100

5 Claims. (Cl. 167--82) This invention relates to tablets and other individual dosage forms. More particularly the invention is concerned with an economical, time-saving process for sugar coating core tablets.

Tablet coating is an old art in which traditional methods have remained essentially unchanged although in recent years some steps have been made toward reducing the tedious and time-consuming operation. Thus, a tablet or compressed pellet is sized with a water repellent resin such as shellac or zein and the resultant tablet 0r pellet is then subcoated with several coats of a material such as gelatin or acacia along with subcoating powders designed for dusting the subcoats. The subcoating operation although time consuming and expensive has been considered necessary in order to round and shape the tablet preparatory to applying a sugar coating with or without added coloring. After further finishing and polishing there is obtained a pharmaceutically elegant tablet but the inordinate amount of time required in the application and drying of the numerous coats including subcoating, color coating and smoothing coat maks the production of such tablets quite expensive.

In comparatively recent times various film coating procedures have been introduced and these methods have materailly reduced the time required to prepare a finished tablet. However, the film coating procedures suffer from a number of disadvantages which in certain instances outweigh the time-saving advantages. For example, the filmforming materials being organic in nature require the use of organic solvents, e.g., alcohol, acetone, ether etc., which are flammable and toxic. It is therefore necessary to carry out the process in explosion-proof equipment with provision for adequate ventilation and exhaust.

Further complications to the well-known tabletting procedures are introduced when it is desired to color the tablet for purposes of distinctiveness or identification. For many years only dyes of the soluble type were used and this necessarily limited the number and range of colors that could be used. In recent times insoluble dyes or lakes have been incorporated into coloring compositions by the use of surfactants to maintain the dyes or lakes in suspension and more recently it has been found that the surfactant was unnecessary. These improvements materially reduced the operating time for coloring solids but the time-consuming subcoating of the tablets was still carried out.

According to the present invention core tablets, that is, tablets which may be sealed, sized or enteric coated but not rounded, are sugar coated in one-quarter to one-third the time required by any previously known method. Utilization of the compositions and process of the invention greatly reduces the operating time by eliminating completely subcoats and smoothing coats hitherto believed necessary.

Additionally, a color, either water-soluble or waterinsoluble, can be incorporated at any stage to give a stable, pharmaceutically elegant finished tablet for which the color is reproducible from batch to batch or operator to operator. There is no necessity for subcoating the rough core tablet or applying smoothing coats yet the finished tablet has stability upon aging, resistance to cracking during sudden temperature changes and a pleasing appearance 7O comparable with tablets made by conventional procedures.

Patented May 25, 1965 The compositions useful in the process of the invention are comprised of an adhesive aqueous suspending medium such as a gelatin solution or preferably a syrup solution and an opaque non-toxic, pharmaceutically acceptable water insoluble pigment as for example titanium dioxide, iron oxide, barium sulfate and calcium carbonate, and if desired a non-toxic dye of either the water-soluble or water-insoluble type.

The aqueous suspending medium is preferably a syrup solution, e.g., an aqueous sugar solution such as an aqueous solution of glucose, lactose, maltose or sucrose. The preferred syrup or sugar solution is a sucrose solution although other sugar derivatives such as mannitol and sorbitol can be used.

The compositions useful in carrying out the improved process can, if desired, contain coloring materials which are any of the non-toxic dyes, lakes and pigments which have been certified for use in the food, drug and cosmetic industries. For example, water-soluble dyes as illustrated by PD & C Yellow No. 5, water-insoluble dyes and lakes as illustrated by .D & C Green No. 5 and pigments as illustrated by yellow, brown, red and black iron oxides, titanium dioxide and barium sulfate are suitable as colorants.

The method of coating core tablets in accordance with the invention comprises forming the syrup or sugar solution in which is suspended the opacifying material by the use of suitable mixing equipment. The suspension is then added to core tablets in a rotating coating pan and the appropriate number of coats applied with air drying after each coat. At any stage colors of the type described above can be added if desired by adding the appropiate color to the syrup and applying the number of coats necessary to give the desired coloring.

The following examples will further illustrate the invention, without however limiting the latter thereto.

Example 1 Coating suspensions incorporating various dyes were prepared as follows:

(A) Grams FD & C Yellow No. 5 0.20

Titanium dioxide, N.F. 7.20

Sucrose (as 70% syrup) 360.00

PD 8.: C Blue No. 1 0.07

Titanium dioxide, N.F. 7.20

Sucrose (as 70% syrup) 360.00

PD & C Yellow No. 6 0.22

Titanium dioxide, N.F. 7.20

Sucrose (as 70% syrup) 360.00

FD & C Red No. 4 0.25

Titanium dioxide, N.F. 7.20

Sucrose (as 70% syrup) 360.00

Mapico Black 0.72

Titanium dioxide, N.F. 7.20

Sucrose (as 70% syrup)- 360.00

Mapico Black 0.36

Brown iron oxide 7.20

Sucrose (as 70% syrup) 360.00

The dyes and pigments were suspended in the syrup and thoroughly mixed. Each of the coloring compositions was added to sized unrounded placebo tablets in a rotating pan until the tablets were evenly covered. The result- Example 2 Grams Titanium dioxide, NF. 14.0 Sucrose (as 70% syrup) 800.0

The above suspension was applied to a run of sized, unrounded oxypertine tablets rotating in a coating pan. A total of 40 mg. per tablet of the coating composition Was applied in about two and one-half hours to give a white sugar coated tablet equal in quality to oxypertine tablets coated in the conventional in five hours.

Example 3 Kilograms Brown iron oxide 0.232

Vanillin 0.004 Sucrose (as 70% syrup) 9.200

A suspension of the above ingredients was applied to a run of size, unrounded pancreatin-containing digestant tablets sold under the trademark Doxegest rotating in a coating pan. Application of the coating composition required about two and one-half hours and the resultant brown tablet was comparable to subcoated Doxegest tablets and required about one-third the time.

Example 4 Grams Titanium dioxide, NF. 2.80 FD & C Yellow No. 5 .062

Sucrost (as 70% syrup) 250.00

A suspension of the above ingredients was applied to a run of sized, unrounded cold tablets containing phenylephrine sold under the trademark Neosynephrine, acetyl p-aminophenol and vitamin C rotating in a coating pan. A total of 125 mg. per tablet was applied in about two and one-half hours. The yellow tablet thus obtained was equal in quality to sized, unrounded cold tablets coated in the conventional manner in six hours.

I claim:

1. .A method of coating tablets which comprises repeatedly adding portions of an aqueous suspending medium containing a non-toxic pharmaceutically acceptable pigment to sized, unround tablets rotating in a coating pan.

2. The method of claim 1 in which the pigment is selected from the group consisting of titanium dioxide, calicum carbonate, barium sulfate and iron oxide.

3. The method of claim 1 in which the aqueous suspending medium is a syrup solution.

4. The method of claim 1 in which a member of the group consisting of water-soluble and water-insoluble dyes is incorporated in the aqueous suspending medium.

5. The method according to claim 1 in which the aqueous suspending medium comprises a sucrose solution containing titanium dioxide and a colorant, and

.drying the finished tablets.

References Cited by the Examiner UNITED STATES PATENTS 9/62 Ralf 16782 9/64 Jeffries 16782 

1. A METHOD OF COATING TABLETS WHICH COMPRISES REPEATEDLY ADDING PORTIONS OF AN AQUEOUS SUSPENDING MEDIUM CONTAINING A NON-TOXIC PHARMACEUTICALLY ACCEPTABLE PIGMENT TO SIZED, UNROUND TABLETS ROTATING IN A COATING PAN. 